Guadalcanal, Battle of(August 1942–February 1943), series of World War II land and sea clashes between Allied and Japanese forces on and around Guadalcanal, one of the southern Solomon Islands, in the South Pacific. Japanese troops had landed on Guadalcanal on July 6, 1942, and had begun constructing an airfield there. On August 7, in the Allies’ first major offensive in the Pacific, 6,000 U.S. Marines landed on Guadalcanal and seized the airfield, surprising the island’s 2,000 Japanese defenders. Both sides then began landing reinforcements by sea, and bitter fighting ensued in the island’s jungles. The Japanese forces on the island reached a peak strength of 36,000 troops by October, but they were unable to overwhelm the Americans’ defensive perimeter and retake the airfield. Six separate naval battles were also fought in the area as the navies of both sides sought to land reinforcements. By November, the U.S. Navy was able to land reinforcements on Guadalcanal faster than were the Japanese, and by January 44,000 U.S. troops were on the island. By February 1943 the Japanese, badly outnumbered, were forced to evacuate 12,000 of their remaining troops from Guadalcanal. Along with the naval Battle of Midway (June 3–6, 1942), the fighting on Guadalcanal marked a turning point in favour of the Allies in the Pacific War.

The Japanese lost a total of 24,000 men killed in the Battle of Guadalcanal, while the Americans sustained 1,600 killed, 4,200 wounded, and several thousand dead from malaria and other tropical diseases. The various naval battles cost each side 24 warships: the Japanese lost 2 battleships, 4 cruisers, 1 light carrier, 11 destroyers, and 6 submarines, while the Americans lost 8 cruisers, 2 heavy carriers, and 14 destroyers.